Many oil wells employ a rod pump for pumping well fluid to the surface. A string of sucker rods extends from a pump jack at the upper end of the well to a reciprocating pump located in the well below the well fluid level. The pump jack strokes the rods and thus the pump upward and downward to lift well fluid to the wellhead.
Some wells have a vertical upper portion that curves into an inclined lower section that may even be horizontal. Placing the pump in the inclined lower section is a problem because the rod string would have to bend through the bend in the well casing and tubing. As the rod string moves up and down in the well, wear occurs on the rod string and well as the tubing in which it extends.